Electrical Test Methods Research Articles

A Review of the Electrical Conductivity Test Methods for Conductive Fabrics

With the substantial growth of the smart textiles market, electrical properties are becoming a basic requirement for most of the advanced textiles used in the development of wearable solutions and other textile-based smart applications. Depending on the textile substrate, the test method to determine the electrical properties can be different. Unlike smart fibers and yarns, the characterization of the electrical properties of fabrics cannot be tested between two connection points because the result would not represent the behavior of the entire fabric, so the electrical properties must be related to an area. The parameters used to characterize the electrical properties of the fabrics include resistance, resistivity, and conductivity. Although all of them can be used to indicate electrical performance, there are significant differences between them and different methods available for their determination, whose suitability will depend on the function and the textile substrate. This paper revises the main parameters used to characterize the electrical properties of conductive fabrics and summarizes the most common methods used to test them. It also discusses the suitability of each method according to several intervening factors, such as the type of conductive fabric (intrinsically or extrinsically conductive), its conductivity range, other fabric parameters, or the final intended application. For intrinsically conductive woven fabrics, all the methods are suitable, but depending on the requirements of conductivity accuracy, the contact resistance from the measuring system should be determined. For intrinsically conductive knitted fabrics, two-point probe, Van der Pauw, and eddy current methods are the most suitable. And for intrinsically conductive nonwoven fabrics, two-point probe and four-point probe methods are the most appropriate. In the case of extrinsically conductive fabrics, the applied method should depend on the substrate and the properties of the conductive layer.

Study of ordered phase precipitation behaviour and hardening mechanism of Au-20Ag-10Cu alloy during deformation-aging treatment

With the rapid development of aerospace technology, the demand for a longer service life of Au-Ag-Cu alloy as conductive slip rings is increasing. Therefore, it is important to improve the hardness of the alloys in order to prolong their service life. Deformation-aging can improve the hardness of many alloys. The effect of the deformation-aging process of Au-20Ag-10Cu (wt%) alloy was investigated on the microstructure and properties, which characterized by DSC(Differential Scanning Calorimeter), XRD(X-ray Diffraction), EBSD(Electron Backscatter Diffraction), TEM(Transmission Electron Microscope) characterization techniques, microhardness and electrical conductivity testing methods. The results indicated that the microhardness increases and the conductivity decreases gradually with the increase of deformation rate. As the aging time increasing, the content of face-centered tetragonal AuCu I ordered phase increases, and thus the hardness increases gradually. The maximum hardness value of 307.44 HV was obtained after undergoing 70 % deformation and then aged at 300 ℃ for 16 h with the electrical conductivity values of 8.40 MS·m−1. This result indicated that both higher hardness and higher electrical conductivity of Au-20Ag-10Cu (wt%) alloy could be obtained, which ensures the requirements in the field of electrical contact materials.

Unraveling quench dynamics and real-time continuous detection in HTS tapes through distributed fiber optic sensing

High-temperature superconducting (HTS) tapes, coils, and magnets often experiences intricate quench instabilities and failures during high current-carrying operations, posing challenges to their practical applications. This study addresses the need for a measurement approach capable of monitoring multi-field signals in superconducting structures within cryogenic and extreme electromagnetic environments. We explore the application of distributed fiber optic sensing (DFOS) technology, specifically employing the optical frequency domain reflectometry scheme, which offers distinct advantages over traditional point-type electrical testing methods, particularly for superconducting materials and magnets. In this experimental study, we continuously track the quench evolution process in superconducting tapes using both bonded and stress-free fibers for real-time monitoring. A comprehensive analysis of the acquired temperature and thermoelastic strain profiles provides essential insights into the dynamic behavior of quench events. The findings demonstrate the effectiveness of DFOS in identifying and characterizing the onset and propagation of quenches. By arranging bonded and stress-free fibers in parallel on the HTS tape’s surface, we successfully decouple the effects of strain-temperature cross-sensitivity, enabling the extraction of temperature and train profiles. The bonded fiber optic sensor demonstrates rapid sensitivity to the thermally quenched events. Temporal derivatives of voltage and thermal strain exhibit characteristic plateaus and slope changes during quenches, respectively. The voltage rate displays two plateaus corresponding to superconducting-to-normal transitions, while strain rates exhibit potential as criteria for identifying quench events in HTS materials. Moreover, DFOS outperforms traditional terminal average voltage measurement, capturing quench evolution tails from the initial point of quench until the complete transition of the segment into the normal state. This experiment provides a solid foundation for further exploration of the underlying quench mechanism.

Assessment of Pulpal Oxygen Saturation in Caries-free and Carious Maxillary Primary Central Incisors Using a Customized Dental Pulse Oximeter.

Pulpal status is best determined by assessing the pulp vitality, which proves to be important yet sceptical with the use of conventional thermal and electrical testing methods. The use of pulse oximetry helps to arrive at a definitive diagnosis by detecting the pulpal oxygen saturation. To assess and compare the pulpal oxygen saturation in caries-free and carious maxillary primary central incisors using a customized dental pulse oximeter sensor probe. A total of 225 maxillary primary central incisors were selected from children aged 3-6 years. Teeth were categorized into group I-caries-free teeth, group II-deep caries lesion, and group III-pulpectomized teeth (n =75 in each group). Pulpal oxygen levels were assessed using a three-dimensionally (3D) designed custom-made probe, and the readings were tabulated. The values were subjected to statistical analysis using paired t-test, analysis of variance (ANOVA), and Tukey's HSD post hoc test. The mean oxygen saturation levels of teeth in group I (92.03%) were statistically significantly high compared to group II (64.36%), that was statistically significant. Readings noted from group III, which was kept as control, was 0%. The obtained results showed that the caries-free group exhibited higher saturation compared to the carious group. 3D designed customized pulse oximeter can be used as an adjunct to assess the pulp vitality in primary teeth. Kanumuru KR, Solomon N, Ramkumar H, et al. Assessment of Pulpal Oxygen Saturation in Caries-free and Carious Maxillary Primary Central Incisors using a Customized Dental Pulse Oximeter. Int J Clin Pediatr Dent 2023;16(4):560-564.

Implementation and Evaluation of a Complex Pumped-Storage Hydropower Plant with Four Units, Common Penstock, and Surge Tank in a Real-Time Digital Simulator

The demand for energy storage systems is rising together with the proportion of renewable energy sources (RES) in power systems. The highest capacity among the various energy storage systems in power systems is provided by pumped-storage hydropower (PSH). In this paper, the ability of the real-time digital simulator (RTDS), e.g., dSpace–SCALEXIO, to emulate a complex pumped-storage hydropower plant with four units, two common penstocks, a surge tank, and a long headrace tunnel is investigated. The RTDS is the smart brain of an advanced lab setup called power hardware in the loop (PHIL), which is an extremely safe and useful lab system for electrical power system research and testing hardware and methods under various conditions. In this research, the capability of an RTDS to emulate the behavior of a pumped-storage hydropower plant including four Francis pump-turbines, four short penstocks, two common penstocks, a surge tank, and a long headrace tunnel is evaluated. Francis pump-turbines are modelled based on the hill chart-based interpolation and waterways including penstocks and headrace tunnel are modelled based on the polynomial approximation of a hyperbolic function. Finally, the results from the RTDS are presented and discussed. According to the results of the paper, we confirm that the RTDS can accurately emulate the hydraulic, mechanical, and electrical transients of a pumped-storage hydropower plant with a complex configuration.

Assessment of the Nubian aquifer characteristics by combining geoelectrical and pumping test methods in the Omdurman area, Sudan

The recent research is carried out to model the characteristics and productivity of the groundwater aquifer in the Omdurman area, Sudan, by combining electrical resistivity and pumping test methods. Omdurman is the most populous city known as the traditional capital of Sudan. Vertical electrical sounding (VES) survey using Schlumberger array is carried out along four profiles to delineate the potential groundwater zones. Application of 1D geophysical inversion revealed five geoelectric layers, including recent deposits, clay, silicified and ferruginous sandstone, and sandstone. Additionally, based on the outcome of VES inversion, Dar Zarrouk parameters, including transverse resistance and longitudinal conductance, were calculated to model the aquifer characteristics. The transverse resistance ranged from 5587 to 309,853 Ωm2, while the longitudinal conductance varied between 0.14 and 2.5 Ω−1. The hydraulic conductivity and transmissivity are further measured using the VES data, ranging from 1.4 to 5.2 m/d and 435 to 1564 m2/day, respectively. The step-drawdown pumping tests were performed to evaluate the aquifer characteristics and thus validate the result of the geoelectrical method. The transmissivity obtained from the step test varied between 583 and 1226 m2/day, showing an acceptable agreement with those of geoelectrical data. Based on the measured parameters, the aquifer is classified as highly productive and ideal for groundwater development. The step drawdown test was further used to assess the performance of groundwater wells. The results indicated that faulty well design and inappropriate pumping rates influence some wells in the study area, resulting in high drawdown and low well efficiency. Overall, the objectives of the study were successfully achieved; nonetheless, detailed hydrogeological and geophysical investigations are recommended for comprehensive evaluation of the groundwater aquifer.

A Computer Vision-Based Quality Assessment Technique for R2R Printed Silver Conductors on Flexible Plastic Substrates

The demand for flexible large-area optoelectronic devices has been growing significantly during recent years. Roll-to-roll (R2R) printing facilitates the cost-efficient industrial production of different optoelectronic devices. Nonetheless, the performance of these devices is highly dependent on the printing quality and number of defects of R2R printed conductors. The image processing technique is an efficient nondestructive testing (NDT) methodology used to detect such defects. In this study, a computer vision-based assessment tool was utilized to visualize R2R printed silver conductors’ defects on flexible plastic substrates. A multistage defect detection technique was proposed to detect and classify both printing-induced defects and imperfections as well as the misalignment of the printed conductors with respect to the reference design. The method proved to be a very reliable approach that can be used independently or in conjunction with electrical testing methods for quality assurance purposes during the production of R2R prints.

A novel evaluation method for in situ space debris detection based on conductive traces

To enable the detection of micrometeoroids and small-sized space debris (MMSD) in the sub-mm range, in situ detectors aboard a spacecraft are the tool of choice. Unfortunately, only a few projects have been sent to space until today. However, knowledge of the MMSD population is important to keep the reference models up-to-date and gain more insights into factors like the amount of debris and its distribution along certain orbits. This will be crucial for the safety of current and future spaceflight missions. Present-day in situ detection systems mostly rely on impact recognition and characterization using different methods. One of them is the perforation of a special detection area during such an event. These areas consist of one or more layers provided with conductive traces. Any interruption of one of these lines can be recognized using some kind of electrical continuity testing method or the determination of the resistance. This goes along with some drawbacks, like the difficult or even impossible multi-event recognition along one line. The proposed concept relies on a reflectometric approach. In doing so, for example, pulses are being sent along a well-defined transmission line, which is a part of the detection area. Any alteration in the characteristic line impedance, for instance, due to an impact, will generate reflections back into the generator. Their evaluation can provide the location as well as the complex impedance of the perturbation.

Double Cathode Modification Improves Charge Transport and Stability of Organic Solar Cells

Introducing a cathode modification layer is an effective method to obtaining highly efficient organic solar cells (OSCs) and improving their stability. Herein, we innovatively introduced a double cathode modification layer (SnO2/ZnO) into a non-fullerene OSCs based on PM7:IT-4F and explored the mechanisms. The effects of SnO2/ZnO film on charge carriers transfer in OSCs are studied via a variety of electrical testing methods including Photo-CELIV measurements. As a result, a cathode buffer layer with low recombination rate and high carrier mobility could be introduced, which is beneficial to electron transport and collection. The champion device based on the double cathode modification layer acquires an efficiency of 12.91%, obviously higher than that of the single cathode modification layer (SnO2 or ZnO) device. Moreover, The SnO2/ZnO double layer is demonstrated to be of great help in the improvement of device stability, and our work could provide a new inspiration for the preparation of OSCs cathode modification layer.

Comparison between Electrical Resistivity Tomography and Geotechnical Field Data for Characterizing Soil Profiles

Background: Electrical resistivity tests at a project site could be a valuable economical alternative to typical geotechnical soil exploration and a reliable source of data. In the present study, the soil at a constructed underground water tank site in Qassim Region – Saudi Arabia is investigated using the electrical resistivity testing method. Objective: The study aims to compare the results of traditional soil boreholes that were conducted at various stages of the project lifetime with the interpretation of soil resistivity test results. Methods: Eight soil boreholes were drilled at the water tank site to capture the nature of soil layers. The electrical resistivity of soil layers at the site is measured and used to investigate the ground subsurface of the project site. The geophysical software, ZondRes2d is utilized to analyze and interpret the collected data. Results: Both geotechnical soil boreholes and geophysical electrical resistivity tests revealed similar soil profiles with three main layers comprising of backfill material, clay with expansive nature, and weathered limestone and marl. The results of the electrical resistivity tests are also affirmative of available resistance values of different soils in the literature. Conclusion: The study shows that electrical resistivity testing is reliable in capturing the soil nature which presents an attractive tool for preliminary investigation of the soil-related problems of distressed structures.

Evaluation of test procedures for durability and permeability assessment of concretes containing calcined clay

The durability and permeability of concrete could be investigated by different test methods that evaluate various transport mechanisms of water and ions in cement-based materials. This research has investigated the suitability of conventional permeability and durability assessment test methods for evaluating the properties of concrete mixtures containing calcined clays and limestone calcined clay cements (LC3). The water absorption, capillary water sorptivity, water penetration, surface electrical resistivity, rapid chloride ions migration coefficient, chloride ions’ penetration profile, and diffusion coefficient were examined in concrete mixtures. A rapid approximation method has also been proposed to estimate the kaolinite content of clays based on the chemical composition data. According to the results, water absorption test based on BS 1881-122 could not accurately specify the permeability properties of binary and LC3 blends. Further, the initial rate of capillary water absorption had an appropriate correlation with the results of water penetration and electrical resistivity test methods.

Comparison Study of Time Domain Reflectometry (TDR) Measurement Methods for Detecting Wire Interconnect Related Open-Contact and Short-Contact Failures in Power Semiconductor

Open-contact and short-contact are 2 common failures that causing power semiconductor to have electrical malfunctioned. One of the reasons of these failures relate to defective in the wire interconnect. Time domain reflectometry (TDR) is a common method widely used to detect failures in semiconductor devices. This study focused on comparing 3 different TDR measurement methods in detecting wire related open and short failure for power semiconductor, namely Single-Ended method, Single-Pin Grounded method and All-Pin Grounded method. A special custom-made jig is used during the measurements to ensure all the methods are measured under the same conditions. This study shows that all the 3 TDR measurement methods are able to detect wire related open and short failures in power semiconductor. The Single-Pin grounded method is the preferred method because it is easy in term of setup and having the good capability in detecting both open and short failures. Furthermore, the study also shows that the TDR is able to detect the location of open and short failures that is not able to achieve by using the conventional electrical testing method.
 HIGHLIGHTS
 
 Comparison study on Single-Ended, Single-Pin Grounded and All-Pin Grounded TDR measurement methods in detecting open-contact and short-contact failure in power semiconductor
 The study shows Single-Pin Grounded TDR measurement method is the preferred method since it is easy in term of setup and able to detect both the open-contact and short-contact failures
 TDR measurement method is also able to locate the location of open-contact and short-contact failures
 
 GRAPHICAL ABSTRACT

Comparative study of electrical test methods on detecting transformer faults

Condition monitoring of distribution and power transformers is of utmost importance to utilities due to cost effectiveness concerns. The common faults that occur in transformers are short circuits and winding deformation. To date, there are many established test methods used to detect these faults. In this study, three test methods (insulation resistance (IR), transformer turn ratio (TTR), and frequency response analysis (FRA)) were compared to assess their effectiveness in detecting short circuit and winding deformation in a three-phase transformer. Based on the results, the three test methods were found to be capable of detecting short circuits. However, only TTR and FRA can detect winding deformation, and FRA can further indicate which phase is faulty. Therefore, it is concluded that FRA is more effective in detecting short circuit and winding deformation of a three-phase transformer.

Methods and Devices Used in Determining the Quality of Electric Wires Terminal Crimping

In this study, it is planned to investigate the analysis methods and devices used for analysis in the quality determination of terminal crimping in the rapidly developing and growing ready-made electrical cable manufacturing sector. Electric cables are used both in data exchange and transmission of electric current. For this reason, it is always desired that its assembly be done easily and reliably. For this, a connection element called terminal is placed at the end of the cable. This process is called terminal crimping. Terminal crimping can be performed manually with the help of crimping pliers or with semi-automatic or fully automatic machines. However, the process may not always be performed in the desired quality. Losses in data transmission may occur as a result of poor quality crimping. In the transmission of electrical current, undesirable events such as cable heating, explosion, fire may occur as a result of bad contact. For this reason, some quality control devices or test platforms to be designed are needed to determine the quality of the terminal crimping operations. Determination of the crimp quality in existing quality control devices is mainly made by electrical testing, cross-sectional imaging and force analysis methods. In this study, comparative analysis of methods and tools for determining the crimp quality in cable manufacturing industry has been made. Defects that may be encountered in crimp processes and their characteristics are revealed, and the reasons for preference, advantages and disadvantages of destructive/non-destructive quality control techniques are summarized.

Electrical Testing of NSTX-U Inner Poloidal Field Coils

The National Spherical Torus eXperiment—Upgrade (NSTX-U) experienced a series of technical problems during its initial operating campaign leading to an extended outage and recovery period. The final event that necessitated shutdown was a turn-to-turn fault in one of the inner PF coils. Investigation of the coil failure and development of remedial measures has become a major focus of the recovery. It was decided that all three inner PF coil pairs that employed similar design features and were fabricated by the same manufacturer needed to be replaced. To further reduce risk, a prototyping program was initiated to qualify suppliers. Four prospective suppliers of replacement coils were mobilized to produce an identical prototype coil that was similar in characteristics to the PF1A coil. The prototype technical evaluation included a comprehensive set of electrical tests on each of the four prototype coils and before and after destructive sectioning into two halves. This article reports on the electrical test methods and results from prototype testing, along with plans for application to the production coils.

Investigation on Electrical Resistance of Chloride Penetration of Alkali Activated Slag Concrete

Alternating-current method for measuring chloride penetration resistance of concrete, test method for coulomb electric flux and rapid chloride migration coefficient (RCM) were applied to evaluate the resistance of chloride penetration in alkali-activated slag concrete in this paper. At the same time, the applicability of the above three electrical parameters test methods to the alkali slag concrete was discussed. The results show that NaOH activated slag concrete behaves higher resistance to chloride penetration than water glass activated slag concrete. Blend of fly ash increases the porosity of alkali-activated slag concrete and weakens the resistance of chloride penetration. Correlation coefficient between chloride migration coefficient and AC electrical resistivity is 0.99. There are good correlations among the evaluation results of three electrical parameters test methods, and all of them behave sound applicability to alkali-activated slag concrete.

Open Defect Detection in Assembled Circuit Boards With Built-In Relaxation Oscillators

In this article, we propose two kinds of electrical interconnect test methods for production tests and field ones of assembled circuit boards, which are performed prior to and after shipping to market, respectively. For these tests, we also propose a built-in test circuit. The methods we followed are based on the oscillation frequency of a relaxation oscillator (ROsc) embedded in integrated circuits (ICs). The frequency is measured as the number of pulse signals within a specified test time. Using the test methods, open defects at the interconnects between IC pins and a printed circuit board (PCB) are detected that are modeled as a resistor, a capacitor, and an open-circuit fault. We examined the detectability of open defects using the process variations afforded by SPICE simulation. The simulation results show that open defects were detected, modeled as a resistor of 45.8 Ω or above, along with open defects modeled as a capacitor and an open-circuit fault using the production test method. In addition, a resistance increase of 1.2 Ω at defect-free interconnects occurred after shipping to market was detected using the field test method. We also prototyped ICs with embedded ROscs and built an experimental circuit made of the ICs on PCBs. Moreover, we experimentally examined whether open defects could be detected. The results show that with the production test method, open defects modeled as a resistor of 10 Ω or above and modeled as a capacitor and an open-circuit fault can be detected.

STUDY ON PERMEABILITY AND ELECTRICAL RESISTIVITY OF RED CLAY CONTAMINATED BY CU2+


 
 
 In order to study the permeability characteristics of heavy metal ions contaminated red clay and explore the rapid detection of permeability of heavy metal contaminated red clay. Through variable-head permeability test and electrical resistivity test (different voltages and methods), the effects of Cu2+ concentration and initial water content on hydraulic conductivity characteristic and resistivity of contaminated red clay was systematically investigated. The relationship between permeability characteristic and electrical resistivity was further explored by taking Cu2+ concentration and moisture content as the intermediate variable. The obtained results indicate that the different voltage has no obvious effect on the resistivity of the samples. The four-phase electrode method is more accurate than the two-phase electrode method. With increasing Cu2+ concentrations the hydraulic conductivity of specimens increases, however the permeability coefficient of contaminated soil decreases with increasing initial water content. In the resistivity test, with increasing of Cu2+ concentrations and water content, the resistivity of samples presented a downward trend, which is decreased sharply at first and then tended to be gentle. The relationship between hydraulic conductivity and resistivity of contaminated soil showed a good fitting curve no matter in different Cu2+ concentration or in different water content, but the fitting curves of them presented opposite trend.
 
 

Charge dynamics and thermal properties of epoxy based micro and nano hybrid composites at high temperatures

AbstractThis paper presents the effects of the filler type and testing temperature on the charge dynamics and thermal properties of the epoxy resin. The micro‐nano hybrid composites with different content of the micro and nano aluminum nitride (AlN) fillers are fabricated. The morphology of micro‐nano hybrid composites is characterized. Electrical testing and thermal analysis methods are adopted to analyze its electrical and thermal performance. The results show that the space charge accumulation is suppressed and the charge decay process is facilitated in the hybrid composites. The electrical performances of the hybrid composites are enhanced by the nano‐fillers. The apparent mobility and activation energy are decreased with nano‐AlN fillers in the composites at the high temperature. The glass transition temperature and thermal stability of the materials is improved with the nano‐AlN. A hypothetical mechanism is proposed to explain the charge carrier injection and transport of the composites at different temperatures.

Assessment of Concrete Curing Duration using Bulk Electrical Conductivity and Porosity

Controlling permeability of concrete is essential for enhancing durability and, thus, the service life. Concrete permeability is affected by the total volume of permeable voids and the continuity of the capillary pore structure. Even though concrete strength is the typical performance parameter used to define a wet curing duration, it is important to maintain wet curing until concrete develops a discontinuous capillary pore structure with a minimum volume of total permeable voids to assure durability. Therefore, the required wet curing period can be defined as the longest duration out from the (i) time to achieve the specified strength, (ii) time to develop a discontinuous capillary pore structure, and (iii) time to develop a minimum volume of total permeable voids. Since concrete strength evaluation methods are well developed, there is a need for developing procedures to evaluate concrete pore structure characteristics to decide on the wet curing duration. This study investigated the use of bulk electrical conductivity and porosity test methods described in ASTM C1760 and C642 to evaluate the (i) time to develop a discontinuous capillary pore structure and (ii) time to develop a minimum volume of total permeable voids, respectively. The suggested procedure of wet curing duration assessment is demonstrated for two concrete mixes: one with only Type I cement and the other with Type I cement and slag.